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And that's pretty much where LEDs stayed for about a decade: the preserve of very specific applications and used in electronics kits, but not really entering mainstream or widespread use as we see today.
Arguably the next big inflection point came courtesy of the Nichia Corporation in September 1991, when Naruhito Iwasa identified a production-friendly way of creating bright white LEDs through more advanced semiconductor doping techniques.
By revising his methods Iwasa redefined a 100x brighter blue LED in 1993, followed by a pure green version in 1995. Nichia continued to blaze the LED trail, forging the way for all the super-bright white and colour spectrum LEDs we see around us today.
Following the race to produce LEDs in multiple colours, the key focus of research quickly turned to brightness. The modern success of the LED in consumer and industrial applications can be attributed to the continuing evolution of super-bright LEDs, which some experts have noted appear to follow a kind of Moore's Law - becoming twice as bright every 18 months. Today LEDs are being developed that can produce 250 lumens per watt, and progress is extremely rapid.
As a result, our homes and workplaces can now be lit very effectively with LED bulbs. Every traffic signal in the US is now lit by LEDs. Every light in every new production vehicle is soon expected to be an LED rather than an incandescent bulb. New offices and retail buildings are being designed to be 100 per cent LED lit. And the extreme efficiency of LED lighting is allowing solar charged units to illuminate the developing world without the need for mains electricity.
Other than lighting, the most notable use of LEDs in our lives today is undoubtedly the introduction of brighter, more energy efficient screens. Multiple innovations in organic LEDs (OLEDs), which integrate a film of organic compound as the emissive electroluminescent layer, have helped transformed screen technology.
OLEDs do not require a backlight, so manufacturers have been able to produce screens that are thinner, lighter and of far higher contrast to earlier Liquid Crystal Display (LCD) or plasma designs. Our monitors, televisions, laptops, smartphones and tablets are now capable of delivering a picture quality that makes us grin without forcing us to recharge often enough to make us groan.
Fifty years on, lighting purists criticise LED light for not being "warm" enough, especially white light in a domestic setting, but the truth is that the relentless and rapid evolution of the LED makes it too efficient to ignore.
It's likely that the end price of an LED bulb will go down by half between now and 2020, which along with its impressive energy efficiency gains, boosts the LED's economic and green credentials so much higher than incandescent light that for most markets the LED is now a no-brainer. On average an LED bulb uses upwards of 80 per cent less energy than a traditional 60W incandescent bulb*, costs a tenth of the price to run each year, and lasts 50 times as long.
And, in the world of technology, the applications are seemingly endless. Traditional LEDs are used in pretty much every device indicator panel and remote control we use daily, as well as the disc drives of our computers, media players and games consoles.
What's next? With innovation as rapid as that experienced over the last 50 years, you should keep a (shaded) eye out for: huge billboards, multi-screen video walls, medical implants, cryptic watches, modern art, interactive medical centres, tattoos, the open source satellite initiative, and gestural music ware. Also, keep an eye on groups such as the Li-Fi Consortium, who are working on next-generation optical wireless communications. ®
Bootnote
*Although it may be worth noting that in the winter, when buildings are warmed by thermostat-controlled central heating, the energy which the old incandescent bulbs used to "waste" in the form of heat will now be automatically replaced by the heating running a little harder and more often. However gas for the boiler is cheaper than electricity for the lights, and when the heating is off this won't happen (and the air-conditioning, if present, won't have to fight the lights so hard in summertime). - Ed
The amazing magical LED: Has it really been fifty years already?
COMMENTS
Bored of Blue LED now!
Just because Blue was difficult until 10-15 years ago, it's been "trendy" for some time now to light things up blue.
It's horrible, it hurts my eyes, it's unnatural, it doesn't look nice, it's not trendy any more, PLEASE STOP IT, world!
That is all.
Re: Bored of Blue LED now!
It's not "Bored of" it's "Bored WITH".
I hate "Bored of". It's horrible, it hurts my eyes, it's unnatural, it doesn't look nice, it's not trendy any more, PLEASE STOP IT, world!
That is all.
Re: LED lighting instead of fluorescent 'haz mat'
"What colour is the sun? oh yes, it's yellow."
An object's colour we perceive is modified by our brains - particularly with an expectation of something being "white". Photographs often show colour casts because the brain is now accepting what the camera media recorded. Cameras that attempt to automatically correct their colour balance will try to render everything as a midday clear sunlight - destroying the atmosphere of sunrise/sunset shots.
So an indoor picture shows the very yellow cast of low temperature lights like candles or tungsten bulbs. It shows green for fluorescent lights. Natural daylight is "high temperature" white. Snow under a clear sky looks blue to a camera. Washing powders used to add blue colouring to fool the eye/brain that the result was "whiter than white". To get the effect of midday sunlight a camera flash has to produce what seems like a very white light to our eyes at the time.
You can see these colour casts in the natural light of a scene - if you look hard. Photographers have long been conscious about vegetation throwing a green pallor on someone's face. However most of the time the eye/brain tends to give us a corrected perception which seems "normal".
Semiconductor diodes always confuse people
"...adding a battery with its positive end connected to the free electron 'n' side of the diode, and the negative end connected to the extra holes 'p' side, things change. The 'n' side electrons are attracted to the positive electrode, and the 'p' side holes are attracted to the negative electrode."
That is a reverse biased diode; no current flows and the depletion zone increases in thickness. As you say :
"No current flows because both the electrons and the holes are moving away from each other. But the depletion zone increases, ......"
But then ...
".... and the interaction between the electrons and the holes releases energy in the form of photons - which generate light."
No. There is no interaction because the electrons and holes move away from each other to opposite ends of the diode, like shy boys and girls at a dance.
It is when the diode is forward biased, with the battery anode connected to the 'p' side and the battery cathode connected to the 'n' side that current flows. Electrons are injected into the 'n' material and flow towards the depletion zone, thus reducing its thickness; 'holes' are effectively created in the 'p' side and flow towards the depletion zone (reducing its thickness to zero), where they combine with the electrons - the resulting energy being converted (partly) to light.
Wikipedia has a good diagram of this:
http://en.wikipedia.org/wiki/File:PnJunction-LED-E.svg
Re: LED lighting instead of fluorescent 'haz mat'
> I didn't realise how dangerous fluorescent lamps were until recent years.
Dangerous? How? Are you referring to all the US scaremongering about the trace of mercury, where people suggest you need a full hazmat-suited contamination squad to clear up a broken bulb? Maybe if you're a building janitor clearing up several smashed bulbs per day you'll take additional precautions, but in a domestic scenario it's a bit like dialling 999 for a papercut.
The biggest problem with compact fluorescent bulbs is that the need for them to fit standard lampholders, which means that the "replaceable" part contains all the electronics to drive the tube. That is unlike traditional fluorescent tubes where the electronics/ballast was in the fixed part of the appliance. Throwing away (or even recycling) the electronics just because the tube has gone is engineering incompetence verging on the criminal. Only a politician could have mandated that.
LEDs aren't much better, although their lifespan mitigates the problem. Plain halogen bulbs are still likely to be the safest and most efficient solution, at least in a climate like the UK.
